Alpha-alumina support and method for preparing the same, silver catalyst for ethylene epoxidation, and ethylene oxidation method

Abstract

The application belongs to the field of catalysts, and relates to an alpha-alumina carrier and a preparation method thereof, a silver catalyst for ethylene epoxidation, and an ethylene oxidation method. The preparation method of the alpha-alumina carrier comprises the following steps: preparing a solid mixture with the following components: trihydro-alpha-Al2O3, pseudo-monohydrate Al2O3, a pore-forming agent, a combustible lubricating material, a fluoride mineralizer, and an alkaline earth metal compound; wherein the pore-forming agent is a non-spherical organic polymer particle; mixing the solid mixture, a binder, and optional water, kneading, and extruding into a shaped body; drying and calcining the shaped body to obtain the alpha-alumina carrier. The application uses different forms of non-spherical organic polymer particles as the pore-forming agent, which has no residue during the calcination of the carrier, and can form a specific pore shape, improve the connectivity between the pores of the carrier, reduce the tortuosity, and improve the permeability, which can significantly improve the activity and selectivity of the catalyst.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of catalysts, and more particularly relates to a preparation method of an alpha-alumina carrier, an alpha-alumina carrier prepared by the preparation method, and a silver catalyst and an ethylene oxidation method prepared by the alpha-alumina carrier. BACKGROUND

[0002] Ethylene oxidation under the action of a silver catalyst mainly generates ethylene oxide, and side reactions also occur to generate carbon dioxide and water. Activity, selectivity and stability are main performance indicators of the silver catalyst. The activity generally refers to the reaction temperature required when a certain reaction load is reached in the production process of ethylene oxide, and the lower the reaction temperature, the higher the activity of the catalyst; the selectivity refers to the ratio of the number of moles of ethylene converted into ethylene oxide to the total number of moles of ethylene in the reaction; and the stability is expressed as the decline rate of the activity and the selectivity, and the smaller the decline rate, the better the stability of the catalyst. At present, silver catalysts can be mainly divided into three types, namely high-activity, high-selectivity and medium-selectivity silver catalysts. Due to the increasingly scarce oil resources and the requirement of energy saving, in recent years, high-selectivity and medium-selectivity silver catalysts are widely used in industrial production and replace the original high-activity silver catalyst.

[0003] The performance of the silver catalyst is not only related to the composition and preparation method of the catalyst, but also related to the performance and preparation method of the carrier used by the catalyst. At present, alpha-alumina is generally selected as the carrier of the silver catalyst. The pores of the alumina carrier can be divided into three types: the first type is the intercrystalline pore of the primary particles, which is mainly the dehydration pore of the alumina raw material crystal grain, and is basically the gap between parallel plate surfaces with a size of 1-2 nm; the second type is the interparticle pore of the alumina raw material, which changes with the escape of water and the change of crystal phase in the calcination, and is a pore with a size of tens of nanometers or more; and the third type is the defect pore and large pore generated during the pore forming agent and the molding of the carrier. The pore structure of the carrier will affect the physical properties, and further affect the performance of the catalyst.

[0004] The pore forming agents used in the preparation of the alumina carrier in the prior art mainly include starch, petroleum coke, carbon powder, sesbania powder, coconut shell charcoal and wood chips. These pore forming agents are usually affected by the production place, and the quality is unstable. Different batches of impurities are introduced into the carrier, and the suitable particle size is usually obtained by crushing, and the particle size distribution range is wide, which is not conducive to realizing the uniform and controllable pore structure of the carrier, and is also not conducive to the performance of the silver catalyst. When the spherical or spherical-like organic polymer particles with uniform and controllable particle size are used as the pore forming agent, there is no residue in the calcination process of the carrier, and the pore structure parameters of the carrier can be adjusted within a certain range, so that the pore size of the carrier presents a unimodal or multimodal distribution, the pore size distribution of a single peak is relatively narrow, but the connectivity between different pores still has a large space for improvement. SUMMARY

[0005] In light of the aforementioned state of the art, the inventors of the present invention have conducted extensive and in-depth research in the field of silver catalysts and their carrier preparation. They have discovered that using non-spherical organic polymer particles of varying morphologies as pore-forming agents leaves no residue during carrier calcination and can form specific pore morphologies, improving pore connectivity, reducing tortuosity, and increasing permeability. Silver catalysts prepared from these carriers, when used in the oxidation of ethylene to produce ethylene oxide, can effectively shorten gas diffusion distances and significantly improve catalytic activity and selectivity. Based on these findings, the present invention provides an α-alumina carrier, a method for its preparation, a silver catalyst for ethylene epoxidation, and an ethylene oxidation method.

[0006] In order to achieve the purpose of the present invention, the first aspect of the present invention provides a method for preparing an α-alumina carrier, comprising the following steps:

[0007] S1. A solid mixture is prepared having the following components: α-A12O3 trihydrate, pseudo-aqueous A12O3, a pore-forming agent, a burnable lubricating material, a fluoride mineralizer, and an alkaline earth metal compound; wherein the pore-forming agent is a non-spherical organic polymer particle;

[0008] S2. The solid mixture in step S1, the binder and optionally water are mixed, kneaded and extruded to obtain a molded body;

[0009] S3. Drying and calcining the molded body in step S2 to obtain the α-alumina support.

[0010] The second aspect of the present invention provides an α-alumina carrier prepared by the preparation method.

[0011] A third aspect of the present invention provides a silver catalyst for ethylene epoxidation, the silver catalyst comprising the following components:

[0012] a) the α-alumina support;

[0013] b) an active component, silver, deposited on component a);

[0014] c) alkali metals and / or alkaline earth metals, or compounds based on alkali metals and / or alkaline earth metals;

[0015] d) rhenium metal and / or rhenium-based compounds; and

[0016] e) Optionally, a rhenium co-promoter selected from at least one metal selected from chromium, molybdenum, tungsten and manganese, and / or selected from compounds based on at least one metal selected from chromium, molybdenum, tungsten and manganese.

[0017] The fourth aspect of the present application provides an ethylene oxidation method, which comprises: subjecting ethylene to ethylene epoxidation reaction under the action of the alpha-alumina carrier and / or the silver catalyst to obtain ethylene oxide.

[0018] The present application uses different morphological non-spherical organic polymer particles as pore-forming agents, which do not remain in the carrier during calcination and can form specific pore morphologies, improve the connectivity between carrier pores, reduce tortuosity and improve permeability. Compared with the prior art, the silver catalyst prepared from the alpha-alumina carrier provided by the present application can effectively shorten the gas diffusion distance and significantly improve the activity and selectivity of the catalyst when used for ethylene oxidation to prepare ethylene oxide.

[0019] Other features and advantages of the present application will be described in detail in the following specific embodiments. DETAILED DESCRIPTION

[0020] The specific embodiments of the present application are described in detail below. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present application, and are not used to limit the present application.

[0021] The endpoints of the ranges and any values disclosed herein are not limited to the precise values stated. The endpoints of the ranges and the values are approximate values and should be understood to include values approximately near these ranges and values within these ranges. For ranges of values, the endpoints of the ranges are combined with the individual points to form new ranges that are within the scope of the present application.

[0022] To achieve the object of the present application, the first aspect of the present application provides a preparation method of an alpha-alumina carrier, comprising the following steps:

[0023] S1. Preparing a solid mixture comprising trihydrate alpha-A12O3, pseudo-monohydrate A12O3, pore-forming agent, combustible lubricating material, fluoride mineralizer and alkaline earth metal compound; wherein the pore-forming agent is a non-spherical organic polymer particle;

[0024] S2. Mixing the solid mixture in step S1, a binder and optionally water, kneading and extruding to obtain a shaped body;

[0025] S3. Drying and calcining the shaped body in step S2 to obtain the alpha-alumina carrier.

[0026] The inventors of the present application found that using different morphological non-spherical organic polymer particles as pore-forming agents, which do not remain in the carrier during calcination and can form specific pore morphologies, improve the connectivity between carrier pores, reduce tortuosity and improve permeability.

[0027] In the present application, "optional water" means that water can be added or not added, and the water here refers to the additional water, not including the water contained in other components.

[0028] According to the present application, in step S3, the drying and calcining method can be performed according to the conventional method in the art. Preferably, the shaped body can be dried to contain 10 wt% or less of free water, the drying temperature can be 80-120°C, and the drying time can be controlled to 1-24 hours according to the moisture content. The calcining makes the alumina completely convert into a-A1203, and the calcining time can be 1-20 hours, preferably 2-15 hours; the maximum calcining temperature can be 1200-1500°C. The calcining makes the alumina completely convert into a-A1203.

[0029] According to the present application, preferably, the non-spherical organic polymer particles are at least one of various shaped particles, more preferably, the non-spherical organic polymer particles are at least one of rod-shaped particles, peanut-shaped particles, dumbbell-shaped particles, snowman-shaped particles, mushroom cap-shaped particles, multi-headed particles, disc-shaped particles, particles with concave-convex edges, and particles with protruding rods.

[0030] According to the present application, preferably, the equivalent diameter of the non-spherical organic polymer particles is 0.5-50 μm, preferably 2-30 μm.

[0031] According to the present application, preferably, the organic polymer forming the non-spherical organic polymer particles is at least one selected from polystyrene (PS), polymethyl methacrylate (PMMA), polyvinyl alcohol (PVA), butyl acrylate-methyl methacrylate copolymer, and styrene-methyl methacrylate copolymer.

[0032] According to the present application, preferably, the amount of the non-spherical organic polymer particles added is 0.1-20 wt% of the total weight of the solid mixture, preferably 1.0-15 wt%.

[0033] According to the present application, preferably, the particle size of the trihydrate a-A1203 is 25-300 μm; and the amount of the trihydrate a-A1203 added is 10-85 wt% of the total weight of the solid mixture, preferably 20-82 wt%.

[0034] According to the present application, preferably, the particle size of the pseudo-monohydrate A1203 is less than 100 μm; and the amount of the pseudo-monohydrate A1203 added is 10-55 wt% of the total weight of the solid mixture, preferably 15-45 wt%.

[0035] In the present invention, the pseudo-monohydrate Al2O3 reacts with acid during the kneading process and is converted into a sol, which acts as a binder. It is also converted into stable α-Al2O3 during the high-temperature roasting process and becomes a part of the α-Al2O3 carrier.

[0036] According to the present invention, preferably, the burnable lubricating material is vaseline and / or white oil; the added amount of the burnable lubricating material is 0.01 to 8.0 wt %, preferably 0.1 to 5.0 wt %, of the total weight of the solid mixture.

[0037] According to the present invention, the addition of the burnable lubricating material is to make the kneaded material easy to shape and granulate. At the same time, an oxidation reaction occurs during the roasting process of the material, and the generated gas escapes. When the carrier is prepared, no impurities are introduced or as little as possible is introduced, thereby not affecting the performance of the catalyst.

[0038] According to the present invention, preferably, the fluoride mineralizer is at least one of hydrogen fluoride, aluminum fluoride, ammonium fluoride, magnesium fluoride, and cryolite; the amount of the fluoride mineralizer added is 0.05-8.0 wt%, preferably 0.5-5.0 wt%, of the total weight of the solid mixture.

[0039] According to the present invention, preferably, the alkaline earth metal compound is at least one of oxides, nitrates, acetates, oxalates and sulfates of strontium and / or barium; the amount of the alkaline earth metal compound added is 0.01 to 5.0 wt%, preferably 0.05 to 2.0 wt%, of the total weight of the solid mixture.

[0040] According to the present invention, preferably, the binder is an acid, and the acid is provided in the form of an aqueous acid solution, preferably an aqueous nitric acid solution, and the weight ratio of nitric acid to water in the aqueous nitric acid solution is 1:(1.25-10); the amount of the binder is 25-60wt% of the total solid mixture.

[0041] According to the present invention, in step S2, the solid mixture obtained in step S1 and the binder are kneaded with optional water. The binder and the pseudo-monohydrate Al2O3 in the mixture form an aluminum sol, which binds the components together to obtain a paste. The paste is then extruded to obtain a molded body. The amount of the binder added can be the conventional amount used in the art. Specifically, preferably, the amount of the binder added is 25 to 60 wt % of the total weight of the solid mixture based on the total weight of the solid mixture. In the present invention, the type of the binder is well known to those skilled in the art, for example, including an acid, which is generally provided in the form of an aqueous acid solution, preferably an aqueous nitric acid solution, wherein the weight ratio of nitric acid to water in the aqueous nitric acid solution is preferably 1:(1.25 to 10).

[0042] According to the present invention, preferably, the binder and pseudo-monohydrate Al2O3 are provided in whole or in part in the form of aluminum sol.

[0043] The second aspect of the present invention provides an α-alumina carrier prepared by the preparation method.

[0044] According to the present invention, preferably, the α-alumina carrier has the following characteristics: α-A12O3 content is more than 90%; crushing strength is 30 to 280N / grain, preferably 80 to 180N / grain; specific surface area is 0.3 to 2.5m 2 / g, preferably 1.0 to 2.2 m 2 / g; water absorption rate is 30-75%, preferably 50-70%; pore volume is 0.30-0.90 ml / g, preferably 0.45-0.70 ml / g; tortuosity is 4-10, preferably 4-7; permeability is 30-200 mdarcy, preferably 50-200 mdarcy.

[0045] In the present invention, the crushing strength of the carrier is measured by a DLⅡ intelligent particle strength tester, and a carrier sample is selected, and the radial crushing strength is measured and the average value is obtained; the water absorption rate is measured by a boiling method; the specific surface area is measured by a nitrogen physical adsorption BET method; and the pore volume, tortuosity, and permeability are measured by a mercury intrusion method.

[0046] A third aspect of the present invention provides a silver catalyst for ethylene epoxidation, the silver catalyst comprising the following components:

[0047] a) the α-alumina support;

[0048] b) an active component, silver, deposited on component a);

[0049] c) alkali metals and / or alkaline earth metals, or compounds based on alkali metals and / or alkaline earth metals;

[0050] d) rhenium metal and / or rhenium-based compounds; and

[0051] e) Optionally, a rhenium co-promoter selected from at least one metal selected from chromium, molybdenum, tungsten and manganese, and / or selected from compounds based on at least one metal selected from chromium, molybdenum, tungsten and manganese.

[0052] According to the present invention, in the above-mentioned silver catalyst, based on the total weight of the silver catalyst, the mass content of silver is 5-37%, preferably 8-32%; the mass content of alkali metal is 5-3000 ppm, preferably 10-2000 ppm; the mass content of alkaline earth metal is 50-20000 ppm, preferably 100-15000 ppm; the mass content of rhenium metal is 10-2000 ppm, preferably 100-1500 ppm; and the content of co-auxiliary agent is 0-1500 ppm, preferably 0-1000 ppm, calculated as the metal in the co-auxiliary agent.

[0053] The silver catalyst of the present invention can be prepared in a conventional manner by impregnating the above-mentioned α-alumina support with a solution containing a silver compound, an organic amine, an alkali metal promoter, an alkaline earth metal promoter, a rhenium promoter and an optional co-promoter.

[0054] The organic amine can be any organic amine compound suitable for preparing a silver catalyst for ethylene oxide production, as long as the organic amine compound can form a silver amine complex with a silver compound. For example, it can be selected from one or more of pyridine, butylamine, ethylenediamine, 1,3-propylenediamine and ethanolamine, preferably a mixture of ethylenediamine and ethanolamine.

[0055] The alkali metal additive can be a compound of lithium, sodium, potassium, rubidium or cesium or a combination of any two thereof, such as their nitrates, sulfates or hydroxides, or a combination of any two or more of the aforementioned compounds, preferably cesium sulfate and / or cesium nitrate.

[0056] The alkaline earth metal additive can be a compound of magnesium, calcium, strontium, or barium, such as their oxides, oxalates, sulfates, acetates, or nitrates, or a combination of any two or more of the foregoing compounds. It is preferably a compound of barium or strontium, and more preferably barium acetate and / or strontium acetate. The alkaline earth metal additive can be applied to the support before, simultaneously with, or after impregnation with silver, or can be impregnated onto the support after the silver compound has been reduced.

[0057] The rhenium-containing auxiliary agent may be rhenium oxide, perrhenic acid, perrhenate, or a mixture thereof, preferably perrhenic acid and / or perrhenate, such as perrhenic acid, cesium perrhenate, and ammonium perrhenate.

[0058] The co-promoter containing the rhenium promoter can be a compound of any transition metal in the periodic table, or a mixture of several transition metal compounds, preferably one or more of chromium, molybdenum, tungsten, and manganese, and / or a compound based on one or more of these elements, such as one or more of chromic acid, chromium nitrate, tungstic acid, cesium tungstate, molybdic acid, ammonium molybdate, manganese acid, and potassium permanganate. The rhenium promoter and its co-promoter can be applied to the support before, simultaneously with, or after the silver is impregnated, or can be impregnated onto the support after the silver compound has been reduced. The addition of the rhenium promoter and its co-promoter can further improve the activity, selectivity, and stability of the activity and selectivity of the resulting silver catalyst.

[0059] According to a specific embodiment of the present invention, the preparation method of the silver catalyst comprises the following steps:

[0060] (1) impregnating the porous α-alumina support with a solution containing a sufficient amount of a silver compound, an organic amine, an alkali metal promoter, an alkaline earth metal promoter, a rhenium-containing promoter, and a co-promoter;

[0061] (2) filtering off the impregnation liquid and drying the impregnated support; and

[0062] (3) activating the carrier obtained in step (2) in an oxygen-containing mixed gas to prepare the silver catalyst.

[0063] In the preparation of the silver catalyst of the present invention, silver nitrate and ammonium oxalate solution are first mixed to form silver oxalate, which is then dissolved in an organic amine to form a silver amine solution, to which the aforementioned additives are added to form an impregnation solution. The prepared impregnation solution is then used to impregnate the aforementioned α-alumina support, which is then drained and thermally decomposed in an air stream or a nitrogen-oxygen mixture having an oxygen content of no more than 21% by weight (e.g., 8% by weight) at a temperature range of 180-700° C., preferably 200-500° C., for 0.5-120 minutes, preferably 1-60 minutes, to produce the finished silver catalyst.

[0064] A fourth aspect of the present invention provides an ethylene oxidation method, which comprises: subjecting ethylene to an ethylene epoxidation reaction under the action of the α-alumina carrier and / or the silver catalyst to obtain ethylene oxide.

[0065] The present invention will be further described below with reference to the examples, but the scope of the present invention is not limited to these examples.

[0066] In the following examples and comparative examples:

[0067] The initial performance and stability of various silver catalysts were tested using a laboratory reactor (hereinafter referred to as a "microreactor") evaluation device. The microreactor used in the evaluation device is a stainless steel tube with an inner diameter of 4 mm, placed in a heating mantle. The catalyst loading volume is 1 mL, and an inert filler is placed at the bottom to ensure that the catalyst bed is located in the constant temperature zone of the heating mantle.

[0068] The activity and selectivity assay conditions used are shown in Table 1:

[0069] Table 1

[0070]

[0071] When the above reaction conditions are stabilized, the gas composition at the reactor inlet and outlet is continuously measured. The results are corrected for volume shrinkage and the selectivity S is calculated using the following formula:

[0072]

[0073] Among them, ΔEO is the difference in ethylene oxide concentration between the reactor outlet gas and the inlet gas, and ΔCO2 is the difference in carbon dioxide concentration between the reactor outlet gas and the inlet gas. The average of more than 10 groups of test data is taken as the test result of the day.

[0074] The lateral crushing strength of the alumina carrier was obtained by using a DLⅡ intelligent particle strength tester to select alumina carrier samples, measure the radial crushing strength and then take the average value.

[0075] Water absorption: determined by boiling method.

[0076] Specific surface area: measured by nitrogen physical adsorption BET method.

[0077] Pore ​​volume, tortuosity and permeability: measured by mercury intrusion method.

[0078] Examples 1-9 are used to illustrate the preparation of the alumina carrier provided by the present invention.

[0079] Example 1

[0080] 3000g of 25-300μm α-Al2O3 trihydrate, 2400g of pseudo-monohydrate Al2O3 less than 100μm, 300g of shaped polystyrene (PS) particles with protruding rods and an equivalent diameter of 18μm, 120g of aluminum fluoride, and 40g of barium nitrate were mixed in a mixer. The mixture was then transferred to a kneader, and 140g of vaseline and 2000ml of dilute nitric acid (nitric acid:water = 1:5, weight ratio) were added and kneaded into an extrudable paste. The mixture was extruded into seven-hole columns with an outer diameter of 8.0mm, a length of 6.0mm, and an inner diameter of 1.0mm. The columns were then dried at 80-120°C for at least 2 hours to reduce the free water content to below 10%. The kneaded support was placed in a bell-shaped kiln and heated from room temperature to 1400°C over 33 hours. The kneaded support was then calcined at 1400°C for 5 hours to obtain a white α-Al2O3 support. The measured physical properties of the support are shown in Table 2 below.

[0081] Example 2

[0082] 3000g of 25-300μm α-Al2O3 trihydrate, 2400g of pseudo-monohydrate Al2O3 less than 100μm, 60g of shaped polystyrene (PS) particles with protruding rods and an equivalent diameter of 18μm, 120g of aluminum fluoride, and 40g of barium nitrate were mixed in a mixer. The mixture was then transferred to a kneader, and 140g of petroleum jelly and 2000ml of dilute nitric acid (nitric acid:water = 1:5, by weight) were added and kneaded into an extrudable paste. This paste was extruded into seven-hole columns with an outer diameter of 8.0mm, a length of 6.0mm, and an inner diameter of 1.0mm. The columns were then dried at 80-120°C for at least 2 hours to reduce the free water content to below 10%. The kneaded support was placed in a bell kiln and heated from room temperature to 1400°C over 33 hours. The mixture was then calcined at 1400°C for 5 hours to obtain a white α-Al2O3 support. The measured physical property data of the carrier are shown in Table 2 below.

[0083] Example 3

[0084] 3000g of 25-300μm α-Al2O3 trihydrate, 2400g of pseudo-monohydrate Al2O3 less than 100μm, 900g of shaped polystyrene (PS) particles with protruding rods and an equivalent diameter of 18μm, 120g of aluminum fluoride, and 40g of barium nitrate were mixed in a mixer. The mixture was then transferred to a kneader, and 140g of vaseline and 2000ml of dilute nitric acid (nitric acid:water = 1:5, weight ratio) were added and kneaded into an extrudable paste. The mixture was extruded into seven-hole columns with an outer diameter of 8.0mm, a length of 6.0mm, and an inner diameter of 1.0mm. The columns were then dried at 80-120°C for at least 2 hours to reduce the free water content to below 10%. The kneaded support was placed in a bell-shaped kiln and heated from room temperature to 1400°C over 33 hours. The kneaded support was then calcined at 1400°C for 5 hours to obtain a white α-Al2O3 support. The measured physical properties of the support are shown in Table 2 below.

[0085] Example 4

[0086] 3000g of 25-300μm α-Al2O3 trihydrate, 2400g of pseudo-monohydrate Al2O3 less than 100μm, 300g of shaped polystyrene (PS) particles with protruding rods and an equivalent diameter of 2μm, 120g of aluminum fluoride, and 40g of barium nitrate were mixed in a mixer. The mixture was then transferred to a kneader, and 140g of vaseline and 2000ml of dilute nitric acid (nitric acid:water = 1:5, by weight) were added and kneaded into an extrudable paste. This paste was extruded into seven-hole columns with an outer diameter of 8.0mm, a length of 6.0mm, and an inner diameter of 1.0mm. The columns were then dried at 80-120°C for at least 2 hours to reduce the free water content to below 10%. The kneaded support was placed in a bell kiln and heated from room temperature to 1400°C over 33 hours. The mixture was then calcined at 1400°C for 5 hours to obtain a white α-Al2O3 support. The measured physical property data of the carrier are shown in Table 2 below.

[0087] Example 5

[0088] 3000g of 25-300μm α-Al2O3 trihydrate, 2400g of pseudo-monohydrate Al2O3 less than 100μm, 300g of shaped polystyrene (PS) particles with protruding rods and an equivalent diameter of 30μm, 120g of aluminum fluoride, and 40g of barium nitrate were mixed in a mixer. The mixture was then transferred to a kneader, and 140g of vaseline and 2000ml of dilute nitric acid (nitric acid: water = 1:5, weight ratio) were added and kneaded into an extrudable paste. The mixture was extruded into seven-hole columns with an outer diameter of 8.0mm, a length of 6.0mm, and an inner diameter of 1.0mm. The columns were then dried at 80-120°C for at least 2 hours to reduce the free water content to below 10%. The kneaded support was placed in a bell-shaped kiln and heated from room temperature to 1400°C over 33 hours. The kneaded support was then calcined at 1400°C for 5 hours to obtain a white α-Al2O3 support. The measured physical properties of the support are shown in Table 2 below.

[0089] Example 6

[0090] 3000g of 25-300μm α-Al2O3 trihydrate, 2400g of pseudo-monohydrate Al2O3 less than 100μm, 300g of rod-shaped polyvinyl alcohol (PVA) particles with an equivalent diameter of 10μm, 120g of aluminum fluoride, and 40g of barium nitrate were mixed in a mixer. The mixture was then transferred to a kneader, and 140g of vaseline and 2000ml of dilute nitric acid (nitric acid:water = 1:5, by weight) were added and kneaded into an extrudable paste. This paste was extruded into seven-hole columns with an outer diameter of 8.0mm, a length of 6.0mm, and an inner diameter of 1.0mm. The columns were then dried at 80-120°C for at least 2 hours to reduce the free water content to below 10%. The kneaded support was placed in a bell kiln and heated from room temperature to 1400°C over 33 hours. The mixture was then calcined at 1400°C for 5 hours to obtain a white α-Al2O3 support. The measured physical property data of the carrier are shown in Table 2 below.

[0091] Example 7

[0092] Three thousand grams of trihydrated α-A12O3 of 25-300 μm, 24,000 grams of pseudo-monohydrated A12O3 of less than 100 μm, 300 grams of mushroom-cap-shaped polystyrene (PS) particles of 10 μm in equivalent diameter, 120 grams of aluminum fluoride, and 40 grams of barium nitrate were put into a mixer and mixed uniformly, and then transferred into a kneader, 140 grams of vaseline and 2,000 ml of dilute nitric acid (nitric acid: water = 1:5 by weight) were added, and kneaded into a paste which could be extrusion-molded. Extrusion-molded into a seven-hole cylinder having an outer diameter of 8.0 mm, a length of 6.0 mm, and an inner diameter of 1.0 mm, and dried at 80-120°C for more than 2 hours to reduce the free moisture content to less than 10%. The carrier after the knead-molding was put into a bell jar kiln, and calcined at 1,400°C for 5 hours after 33 hours from room temperature to 1,400°C, to obtain a white α-A12O3 carrier. The measured physical properties of the carrier are shown in Table 2.

[0093] Example 8

[0094] Three thousand grams of trihydrated α-A12O3 of 25-300 μm, 24,000 grams of pseudo-monohydrated A12O3 of less than 100 μm, 300 grams of mushroom-cap-shaped polystyrene (PS) particles of 10 μm in equivalent diameter, 120 grams of aluminum fluoride, and 40 grams of barium nitrate were put into a mixer and mixed uniformly, and then transferred into a kneader, 140 grams of vaseline and 2,000 ml of dilute nitric acid (nitric acid: water = 1:5 by weight) were added, and kneaded into a paste which could be extrusion-molded. Extrusion-molded into a seven-hole cylinder having an outer diameter of 8.0 mm, a length of 6.0 mm, and an inner diameter of 1.0 mm, and dried at 80-120°C for more than 2 hours to reduce the free moisture content to less than 10%. The carrier after the knead-molding was put into a bell jar kiln, and calcined at 1,400°C for 5 hours after 33 hours from room temperature to 1,400°C, to obtain a white α-A12O3 carrier. The measured physical properties of the carrier are shown in Table 2.

[0095] Example 9

[0096] A mixture of 3000 g of trihydrated α-A12O3 of 25-300 μm, 2400 g of pseudo monohydrated A12O3 of less than 100 μm, 200 g of anisometric polystyrene (PS) particles of 200 g of 18 μm in equivalent diameter with convex rods, 200 g of rod-shaped polymethyl methacrylate (PMMA) particles of 10 μm in equivalent diameter, 120 g of aluminum fluoride and 40 g of barium nitrate was mixed uniformly in a mixer and transferred to a kneader, 140 g of vaseline and 2000 ml of dilute nitric acid (nitric acid: water = 1:5 by weight) were added and kneaded into a paste which could be extruded into a shape. The paste was extruded into a seven-hole columnar shape of 8.0 mm in outer diameter, 6.0 mm in length and 1.0 mm in inner diameter, dried at 80-120°C for more than 2 hours to reduce the free moisture content to less than 10%, and calcined at 1400°C for 5 hours in a bell jar furnace which was raised from room temperature to 1400°C over 33 hours to obtain a white α-A12O3 carrier. The physical properties of the carrier were measured and are shown in Table 2.

[0097] Examples 10-18 are illustrative of the preparation of silver catalysts provided by the present application.

[0098] Example 10

[0099] A solution of 140 g of silver nitrate was prepared by dissolving it in 150 mL of deionized water, and a solution of 64 g of ammonium oxalate was prepared by dissolving it in 520 mL of deionized water. The two solutions were mixed under vigorous stirring to form a white silver oxalate precipitate which was aged for more than 30 minutes. The precipitate was filtered and washed with deionized water until no nitrate ions were present. The filter cake contained about 60 wt% silver and about 15 wt% water.

[0100] A solution of 140 g of silver nitrate was prepared by dissolving it in 150 mL of deionized water, and a solution of 64 g of ammonium oxalate was prepared by dissolving it in 520 mL of deionized water. The two solutions were mixed under vigorous stirring to form a white silver oxalate precipitate which was aged for more than 30 minutes. The precipitate was filtered and washed with deionized water until no nitrate ions were present. The filter cake contained about 60 wt% silver and about 15 wt% water.

[0101] A 20 g sample of the carrier prepared in Example 1 was placed in a container which could be evacuated, and the container was evacuated to more than 10 mm Hg. The impregnation solution was introduced into the container, and the container was held for 30 minutes. The excess solution was drained. The impregnated carrier was heated in a stream of air at 450°C for 3 minutes, and then cooled to produce silver catalyst C-1.

[0102] Example 11

[0103] Example 11 was repeated except that the carrier sample prepared in Example 2 was used instead of the carrier sample prepared in Example 1. The silver catalyst produced was C-2.

[0104] Example 12

[0105] Example 10, except that the support sample prepared in Example 3 was used in place of the support sample prepared in Example 1. The silver catalyst prepared was C-3.

[0106] Example 13

[0107] Example 10, except that the support sample prepared in Example 4 was used in place of the support sample prepared in Example 1. The silver catalyst prepared was C-4.

[0108] Example 14

[0109] Example 10, except that the support sample prepared in Example 5 was used in place of the support sample prepared in Example 1. The silver catalyst prepared was C-5.

[0110] Example 15

[0111] Example 10, except that the support sample prepared in Example 6 was used in place of the support sample prepared in Example 1. The silver catalyst prepared was C-6.

[0112] Example 16

[0113] Example 10, except that the support sample prepared in Example 7 was used in place of the support sample prepared in Example 1. The silver catalyst prepared was C-7.

[0114] Example 17

[0115] Example 10, except that the support sample prepared in Example 8 was used in place of the support sample prepared in Example 1. The silver catalyst prepared was C-8.

[0116] Example 18

[0117] Example 10, except that the support sample prepared in Example 9 was used in place of the support sample prepared in Example 1. The silver catalyst prepared was C-9.

[0118] Comparative Example 1

[0119] This comparative example was used to illustrate the preparation of a reference alumina support.

[0120] 3000g of 25-300μm α-Al2O3 trihydrate, 2400g of pseudo-monohydrate Al2O3 less than 100μm, 300g of petroleum coke with a median particle size of 18μm, 120g of aluminum fluoride, and 40g of barium nitrate were mixed in a mixer. The mixture was then transferred to a kneader, and 140g of vaseline and 2000ml of dilute nitric acid (nitric acid:water = 1:5, by weight) were added and kneaded into an extrudable paste. This was extruded into a seven-hole column with an outer diameter of 8.0mm, a length of 6.0mm, and an inner diameter of 1.0mm. The column was then dried at 80-120°C for at least 2 hours to reduce the free water content to below 10%. The kneaded support was placed in a bell kiln, heated from room temperature to 1400°C over 33 hours, and calcined at 1400°C for 5 hours to obtain a white α-Al2O3 support. The measured physical property data of the carrier are shown in Table 2 below.

[0121] Comparative Example 2

[0122] This comparative example is used to illustrate the preparation of a reference alumina support.

[0123] 3000g of 25-300μm α-Al2O3 trihydrate, 2400g of pseudo-monohydrate Al2O3 less than 100μm, 300g of uniformly sized spherical polymethyl methacrylate (PMMA) particles with a diameter of 18μm, 120g of aluminum fluoride, and 40g of barium nitrate were mixed in a mixer. The mixture was then transferred to a kneader, and 140g of vaseline and 2000ml of dilute nitric acid (nitric acid:water = 1:5, by weight) were added and kneaded into an extrudable paste. The mixture was then extruded into a seven-hole column with an outer diameter of 8.0mm, a length of 6.0mm, and an inner diameter of 1.0mm. The column was then dried at 80-120°C for at least 2 hours to reduce the free water content to below 10%. The kneaded support was placed in a bell-shaped kiln and heated from room temperature to 1400°C over 33 hours. The kneaded support was then calcined at 1400°C for 5 hours to obtain a white α-Al2O3 support. The measured physical properties of the support are shown in Table 2 below.

[0124] Comparative Example 3

[0125] This comparative example is used to illustrate the preparation of a reference alumina support.

[0126] Three thousand grams of 25-300 μm trihydrated α-A12O3, 24 grams of less than 100 μm pseudo-monohydrated Al2O3, 300 grams of 10 μm equivalent diameter spherical polystyrene (PS) particles, 120 grams of aluminum fluoride and 40 grams of barium nitrate were mixed in a mixer and transferred to a kneader, 140 grams of vaseline and 2000 ml of dilute nitric acid (nitric acid: water = 1:5 by weight) were added and kneaded into an extrudable paste. The paste was extruded into a seven-hole columnar shape having an outer diameter of 8.0 mm, a length of 6.0 mm and an inner diameter of 1.0 mm, and dried at 80-120°C for more than 2 hours to reduce the free moisture content to less than 10%. The kneaded and shaped support was placed in a bell jar kiln, and raised from room temperature to 1400°C over 33 hours, and calcined at 1400°C for 5 hours to obtain a white α-A12O3 support. The physical properties of the support were measured and are shown in Table 2.

[0127] Comparative Example 4

[0128] This comparative example is for the preparation of a reference silver catalyst.

[0129] The same as Example 10 except that the support sample prepared in Comparative Example 1 was used instead of the support sample prepared in Example 1. The silver catalyst prepared was DC-1.

[0130] Comparative Example 5

[0131] This comparative example is for the preparation of a reference silver catalyst.

[0132] The same as Example 10 except that the support sample prepared in Comparative Example 2 was used instead of the support sample prepared in Example 1. The silver catalyst prepared was DC-2.

[0133] Comparative Example 6

[0134] This comparative example is for the preparation of a reference silver catalyst.

[0135] The same as Example 10 except that the support sample prepared in Comparative Example 3 was used instead of the support sample prepared in Example 1. The silver catalyst prepared was DC-3.

[0136] Table 2 Physical properties of the support

[0137]

[0138] The activity and selectivity of the catalyst samples were measured under the aforementioned process conditions using a microreactor evaluation apparatus, and the results of the microreactor evaluation are shown in Table 3.

[0139] Table 3 Performance of the catalyst

[0140]

[0141] The data in Tables 2 and 3 indicate that the support provided by the present invention exhibits reduced tortuosity and increased permeability, indicating enhanced connectivity between the support pores. Catalysts prepared using the support of the present invention exhibit significantly lower reaction temperatures (i.e., increased reactivity) and significantly improved selectivity, demonstrating broad application prospects.

[0142] While various embodiments of the present invention have been described above, the above description is intended to be illustrative, not exhaustive, and not limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments.

[0143] The endpoints of the ranges and any values ​​disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoints of each range, the endpoints of each range and individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered to be specifically disclosed herein.

Claims

1. A method for preparing an α-alumina carrier, characterized in that: The steps include: S1. Preparing a solid mixture comprising: α-Al2O3 trihydrate, pseudo-monohydrate Al2O3, a pore-forming agent, a burnable lubricant, a fluoride mineralizer, and an alkaline earth metal compound; wherein the pore-forming agent is non-spherical organic polymer particles; the non-spherical organic polymer particles are at least one of rod-shaped particles, peanut-shaped particles, dumbbell-shaped particles, snowman-shaped particles, mushroom-cap-shaped particles, multi-headed particles, disc-shaped particles, particles with concave and convex edges, and particles with protruding rods; the non-spherical organic polymer particles have an equivalent diameter of 0.5 to 50 μm; forming the non-spherical organic polymer particles The organic polymer is selected from at least one of polystyrene, polymethyl methacrylate, polyvinyl alcohol, butyl acrylate-methyl methacrylate copolymer and styrene-methyl methacrylate copolymer; the amount of the non-spherical organic polymer particles added is 0.1-20wt% of the total weight of the solid mixture; the amount of the trihydrate α-Al2O3 added is 10-85wt% of the total weight of the solid mixture; the amount of the pseudo-monohydrate Al2O3 added is 10-55wt% of the total weight of the solid mixture; the amount of the burnable lubricating material added is 0.01-8.0wt% of the total weight of the solid mixture; S2. The solid mixture in step S1, a binder and optionally water are mixed, kneaded and extruded to obtain a molded body; S3. Drying and calcining the molded body in step S2 to obtain the α-alumina support.

2. The method for preparing an α-alumina carrier according to claim 1, wherein: The equivalent diameter of the non-spherical organic polymer particles is 2 to 30 μm.

3. The method for preparing an α-alumina carrier according to claim 1, wherein: The amount of the non-spherical organic polymer particles added is 1.0-15 wt % of the total weight of the solid mixture.

4. The method for preparing an α-alumina carrier according to any one of claims 1 to 3, wherein: The particle size of the trihydrate α-A12O3 is 25-300 μm; the amount of the trihydrate α-A12O3 added is 20-82 wt% of the total weight of the solid mixture; The particle size of the pseudo monohydrate Al2O3 is less than 100 μm; the added amount of the pseudo monohydrate Al2O3 is 15~45wt% of the total weight of the solid mixture.

5. The method for preparing an α-alumina carrier according to any one of claims 1 to 3, wherein: The burnable lubricating material is vaseline and / or white oil; the amount of the burnable lubricating material added is 0.1-5.0wt% of the total weight of the solid mixture; The fluoride mineralizer is at least one of hydrogen fluoride, aluminum fluoride, ammonium fluoride, magnesium fluoride, and cryolite; the amount of the fluoride mineralizer added is 0.05-8.0 wt% of the total weight of the solid mixture; The alkaline earth metal compound is at least one of oxides, nitrates, acetates, oxalates and sulfates of strontium and / or barium; and the amount of the alkaline earth metal compound added is 0.01-5.0 wt % of the total weight of the solid mixture.

6. The method for preparing an α-alumina carrier according to claim 5, wherein: The amount of the fluoride mineralizer added is 0.5-5.0 wt % of the total weight of the solid mixture.

7. The method for preparing an α-alumina carrier according to claim 5, wherein: The amount of the alkaline earth metal compound added is 0.05-2.0 wt % of the total weight of the solid mixture.

8. The method for preparing an α-alumina carrier according to any one of claims 1 to 3, wherein: The binder is an acid, which is provided in the form of an acid aqueous solution; the amount of the binder is 25-60 wt % of the total amount of the solid mixture.

9. The method for preparing an α-alumina carrier according to claim 8, wherein: The acid is a nitric acid aqueous solution, and the weight ratio of nitric acid to water in the nitric acid aqueous solution is 1:(1.25-10).

10. The method for preparing an α-alumina carrier according to claim 8, wherein: The binder and pseudo-monohydrate Al2O3 are provided in whole or in part in the form of aluminum sol.

11. An α-alumina carrier prepared by the preparation method according to any one of claims 1 to 10.

12. The α-alumina carrier according to claim 11, wherein The α-alumina carrier has the following characteristics: α-A12O3 content is more than 90%; crushing strength is 30~280N / grain; specific surface area is 0.3~2.5m 2 / g; water absorption rate is 30~75%; pore volume is 0.30~0.90ml / g; tortuosity is 4~10; permeability is 30~200 mdarcy.

13. The α-alumina carrier according to claim 12, wherein The α-alumina carrier has the following characteristics: a crushing strength of 80-180 N / particle; a specific surface area of ​​1.0-2.2 m 2 / g; water absorption rate is 50~70%; pore volume is 0.45~0.70ml / g; tortuosity is 4~7; permeability is 50~200 mdarcy.

14. A silver catalyst for ethylene epoxidation, characterized in that The silver catalyst comprises the following components: a) the α-alumina carrier according to any one of claims 11 to 13; b) an active component silver deposited on component a); c) alkali metals and / or alkaline earth metals, or compounds based on alkali metals and / or alkaline earth metals; d) rhenium metal and / or rhenium-based compounds; as well as e) Optionally, a rhenium co-promoter selected from at least one metal selected from chromium, molybdenum, tungsten and manganese, and / or selected from compounds based on at least one metal selected from chromium, molybdenum, tungsten and manganese.

15. A method for ethylene oxidation, characterized in that: The method comprises: subjecting ethylene to an epoxidation reaction under the action of the silver catalyst described in claim 14 to obtain ethylene oxide.

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